1. Field of the Invention
The present invention relates to an apparatus using a double focusing type fly-back transformer. Particularly, the present invention relates to an apparatus using a double focusing type fly-back transformer, in which a top bleeder type is adopted in drawing the focus voltage of the fly-back transformer instead of the conventional neutral point type, the double patterns of the focus resistors are separated from each other instead of the conventional common connections to the ground on the substrate FUB of a focus unit part, and one or more of the separately installed focus resistor patterns is used as a feedback line together with the bleeder resistor, thereby drastically reducing the size of the substrate of the bleeder resistor.
2. Description of the Prior Art
FIG. 1 is a perspective view showing the external shape of the general double focusing type fly-back transformer. Referring to FIG. 1, the double focusing type fly-back transformer is generally used in televisions and computer monitors to supply an anode voltage, a double focus voltage and a screen voltage. In the double focusing type fly-back transformer 10 of FIG. 1, reference code VOLH indicates an adjusting volume for a horizontal focus voltage, VOLV indicates an adjusting volume for a vertical focus voltage, and VOLG indicates an adjusting volume for a screen voltage. Further, reference code CA0 indicates a cable for supplying an anode voltage to an anode of the monitor, and CA1, CA2 and CA3 indicates cables for supplying a horizontal focus voltage, vertical focus voltage and a screen voltage to respective grids of an electron gun. Reference code CAP indicates an anode cap.
FIG. 2 is a circuit diagram showing the circuital constitution of the apparatus using the conventional double focusing type fly-back transformer. Referring FIG. 2, in the conventional double focusing type fly-back transformer 10, a horizontal outputting part 5 includes a transistor Q1, a damper diode DD and a tuning capacitor CT. The horizontal outputting part 5 operates in accordance with horizontal synchronizing signals to generate pulses in a primary winding L1 of the fly-back transformer. The pulse type ac voltages of the primary winding L1 are stepped up, rectified and flattened by secondary windings L11, rectifying diodes D11-D16 and a high voltage capacitor C11. The fly-back transformer which operates in this manner supplies an anode voltage, and supplies a double focus voltage and a screen voltage through the focus unit part.
The double focusing type fly-back transformer 10 includes: a primary winding L1 with its one end connected to an output terminal of a horizontal outputting part 5, and with its another end connected to a power source B+, for obtaining collector pulses through LC-resonances of the horizontal outputting part 5; secondary windings L11-L16 for stepping up the pulse type ac voltages in accordance with the winding ratios of them to the primary winding L1; rectifying diodes D11-D16 for rectifying the ac voltages of the secondary windings; a high voltage capacitor C11 for flattening the rectified dc voltage; a bleeder resistor BR1 for sensing the CPT (color picture tube) discharge and the high voltage fluctuations at a set-off status; and a focus unit part for supplying two focus voltages (double focus voltage) and a screen voltage by utilizing a neutral point (upon D12) of the secondary windings L11-L16. Further, an iron core FC is disposed between the primary winding L1 and the secondary windings L11-L16.
The focus unit part is used on a large monitor of over 17 inches. This part is a double focus unit for supplying a horizontal focus voltage and a vertical focus voltage, and includes: serially connected fixed and first variable resistors R11 and VR11 for outputting the horizontal focus voltages to a horizontal focus voltage output terminal FH; serially connected fixed and second variable resistors R12 and VR12 for outputting the vertical focus voltages to a vertical focus voltage output terminal FV; and a third variable resistor VR13 connected between the connection point of the resistors R11 and R12 and a grounded first connection pint #11, for outputting the screen voltage to a screen voltage output terminal G2.
Meanwhile, the fly-back transformer 10 further includes: a coupling capacitor CP for outputting parabolic pulses 300V.sub.p-p (supplied from the set through a second connection pin #12) onto the vertical focus voltage (about 4.5 KV-8.5 KV), the vertical voltage being outputted through the vertical focus voltage output terminal FV; and a bypass capacitor CB for bypassing to the ground the ac noise components such as the parabolic pulses contained in the horizontal focus voltage outputted through the horizontal focus voltage output terminal FH.
Further, in order to feed back the voltage to be compensated to the power source B+ in accordance with the high voltage fluctuations after detecting the high voltage fluctuations in the output of the fly-back transformer, the set side includes: a capacitor C13 connected between the ground and a high voltage capacitor C11 through a fourth connection pin #14; a capacitor C12 connected between a capacitor C11 and a bleeder resistor BR1 through a third connection pin #13; an initial voltage setting part 12 for voltage-dividing the anode voltage (a high voltage) through the bleeder resistor BR1 and its internal resistors; and a high voltage stabilizing circuit part 11 for compensating the power source B+ by feeding back the voltage of the initial voltage setting part 12.
FIG. 3 illustrates the printed patterns formed on the substrate FUB of the focus unit part of the double focusing type fly-back transformer of FIG. 2. Referring FIG. 3, the conventional substrate FUB of the focus unit part is a ceramic board, and a resistor PF is formed on the ceramic board. Here, reference codes PCA1-PCA3 indicate connection points for cables CA1-CA3. Reference codes PVOLH, PVOLV and PVOLG indicate volume connection points for adjusting volumes VOLH, VOLV and VOLG. Reference codes PCP and PCB indicate capacitor connection points for the coupling capacitor CP and the bypass capacitor CB. Reference code PD12 indicates a diode connection point to be connected to the diode D12, and P11 indicates a connection point for a first connection pin.
FIG. 4 illustrates the contour of the bleeder resistor BR1 of FIG. 2. Referring to FIG. 4, the conventional bleeder resistor BR1 has dimensions of about 15 mm.times.50 mm, and is formed by forming a printed pattern BRP1 upon a ceramic substrate BRB1. Reference code L13 indicates a lead line to be connected to a third connection pin #13, and LPH indicates a lead line to be connected to a connection point PH of an anode voltage output line. The fly-back transformer contains the bleeder resistor BR1 and the high voltage capacitor C11 with the same sizes. The fly-back transformer further includes the FUB and a bypass capacitor CB and a coupling capacitor CP connected to the FUB.
The conventional double focusing fly-back transformer constituted as above will now be described as to its operations.
First, referring to FIG. 2, the horizontal outputting part 5 which includes the horizontal output transistor Q1, the damper diode DD and the tuning capacitor CT operates within a range of 15-100 KHz in accordance with the horizontal synchronizing signals. The primary winding L1 which is connected between the output terminal of the horizontal outputting part 5 generates pulse type ac voltages. These ac voltage of the primary winding L1 are stepped up by the secondary windings L11-L16, and then, the ac voltages are rectified into a dc voltage. Then this dc voltage is flattened by the high voltage capacitor C11, and thus, a dc voltage of about 26 KV is outputted through an anode voltage output terminal HV to an anode terminal of a monitor or other picture receiving tubes.
Meanwhile, the level of the voltage which is supplied from the neutral point (upon D12) of the secondary windings L11-L16 is decided by the winding ratio of the secondary windings to the primary winding. This voltage (about 10 KV) is divided by the parallelly connected first and second variable resistors VR11 and VR12 and the serially connected third variable resistor VR13. A horizontal focus voltage which has been adjusted to a rated voltage of about 4.5-8.5 KV by the first variable resistor VR11 is outputted through the horizontal focus voltage output terminal FH. Further, a vertical focus voltage which has been adjusted to a rated voltage of about 4.5-8.5 KV by the second variable resistor VR12 is outputted through the vertical focus voltage output terminal FV. Further, a screen voltage which has been adjusted to a rated voltage of about 0.2-1.2 KV by the third variable resistor VR13 is outputted through the screen voltage output terminal G2.
In order to compensate the fluctuation amount of the high voltage supplied from the fly-back transformer, the set includes an initial voltage setting part 12 and a high voltage stabilizing circuit part 11. In the initial voltage setting part 12, the high voltage of about 26 KV is divided by the bleeder resistor BR1 of 600 M.OMEGA. and by the resistors (having a resistance range of 100-250 K.OMEGA.) of the initial voltage setting part 12. Therefore, the high voltage of 26 KV is divided mostly by the bleeder resistor BR1 (600 M.OMEGA.), while only 5 v is divided by the initial voltage setting part 12. Here, if the high voltage fluctuates to above 26 KV, then the initial voltage setting part 12 detects more than 5 v, while if the high voltage fluctuates to below 26 KV, then the initial voltage setting part outputs less than 5 V.
The high voltage stabilizing circuit part 11 compares the detected voltage of the initial voltage setting part 12 with an internal reference voltage (5 V) so as to detect the fluctuations of the high voltage. If the detected voltage is higher than the reference voltage, then a control is carried out such that the power source B+ should be reduced. On the other hand, if the detected voltage is lower than the reference voltage, then a control is carried out such that the power source B+ should be increased. For this purpose, that is, in order to compensate the fluctuations, a compensation voltage is fed back to the power source B+ of the primary winding L1.
In this conventional double focusing type fly-back transformer, the feedback detection voltage is detected from the dc high voltage, and based on the detected voltage, the compensation voltage is decided to supply it to the set. For this purpose, a separate feedback line including a bleeder resistor is required, while in the set, the initial voltage setting part and the high voltage stabilizing circuit part (or IC) are required to feed back the compensation voltage to the power source B+ based on the detected voltage.
However, the bleeder resistor which constituted the feedback line of the double focusing type fly-back transformer is formed by printing a printed pattern BRP1 upon on a ceramic substrate BRB1 as shown in FIG. 4. The bleeder resistor has to have a large resistance value to withstand against a voltage breakdown, and therefore, the length of the printed pattern is extended, while it cannot be printed densely. The substrate BRB1 on which the bleeder resistor of the conventional fly-back transformer is formed becomes very long, and therefore, it occupies a large area within the transformer. As a result, the bulk of the transformer is increased, and therefore, the manufacturing cost is increased, as well as making it impossible to realize a miniaturization. Thus the increase in the product price becomes problematic.